Refrigeration compressor starting unloader



Jan. 4, 1949. J. M. MURPHY 2,458,013 I REFRIGERATION COMPRESSOR STARTING UNLOADBR Filed July 19, 194-4 Patented Jan. 4, 1949 REFRIGERATION COMlRESSOR STARTING UNLoApnR John M. Murphy, Dayton, Ohio, assignor to eral Motors Corporation, Dayton,

ration of Delaware Gen- Ohio, at corpo- Application July 19, 1944. Serial No.\545,642

8 Claims.

This invention relates to refrigerating apparatus and more particularly to an improved motor-compressor arrangement for use in a refrigerator system.

One object of this invention is to provide a simple and inexpensive arrangement for unloading a refrigerant compressor during the starting period of the motor.

More particularly it is an object of this invention to eliminate the need for an unloader valve and to eliminate the need for a powerful unloader operating mechanism.

A further object of this invention is to provide an unloader in which a small pin falls by gravity to unlo..d the compressor and in which the compressor is loaded merely by lifting the pin against the force of gravity.

vStill another object of this invention is to provide an unloader which may be built into a standard compressor without making major alterations andwithout providing extra room for the compressor unloader mechanism.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying' drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. l is a vertical sectional view showing my invention applied to a sealed motor-compressor unit:

Fig. 2 is a horizontal sectional view showing the arrangement of the impeller and the divider block with respect to the compression chamber.

Fig. 3 is a fragmentary sectional view showing a modified compressor unloader azrangement; and

Fig. 4 diagrammatically shows the electrical circuit.

Referring now to Fig. 1, reference numeral indicates a conventional motor compressor casing within which there is suitably mounted a frame element l2 which includes the main shaft bearing It. A motor stator i 6 is carried by the frame 12 as shown. The main drive shaft I8 is journaled within the bearing l4 and has mounted at its upper end a conventional motor rotor 20 which serves to drive the shaft l8. The lower end of the shaft i8 is provided with an eccentric portion 20 which serves to operate the impeller 22 in accordance with well-known practice. The impeller 22 is surrounded by the cylindrical element 2 which is supported between the frame I2 and the compressor end plate 28 as shown.

Divider block 28 is siidably mounted within the slot 30 provided in the wall of the cylindrical element 24. A pair of spring elements 36 normally bias the divider block into sealing engagement with the impeller 22. The springs 36 abut against the element 38 carried by the frame l2 as shown. The elements 24 and 26 may be held in place relative to the frame l2 by any suitable means such as bolts 40. The refrigerant to be compressed enters the compression chamber 44 through the suction line 45 in accordance with standard practice. The compressed refrigerant leaves through the outlet port 48 which, for purposes of illustration, has been shown in the bot,- tom plate 25. a

The motor-compressor mechanism described thus far is intended to represent conventional motor-compressor mechanism. In order to unload the unit for starting purposes I have provided a small hole 50 in the upper side of the divider block 28 and have provided a small pin 52 which is adapted to fall by gravity into the hole 5il'whenever the solenoid 54 is deenergized. The pin 52 is guided within an aperture 55 provided in the frame I2 as shown. For purposes of illustration I have shown an appreciable amount of clearance between the pin 52 and the aperture 55 whereas in actual practice a, smaller amount of clearance would be provided. Enough clearance must be provided however, to allow any fluid below the pin 52 to escape when the pin 52 drops down into the hole 50. During normal pumping operation, the divider block 28 is pushed out by the impeller 22 once during each revolution of the shaft It. It is apparent that when the divider block 28 is in its outer position the pin 52 is free to drop down into the hole 50 so as to hold the divider block in its outer'position thereby unloading the compressor. By virtue of the above described arrangement it is obvious that very little power is required to operate the pin 52. In fact the pin falls by gravity and the only force necessary to lift the pin is that force necessary to overcome the force of gravity tending to hold the pin down. As a consequence of this fact, a very small power source such as an inexpensive high resistance solenoid 54 may be used for operating the unloading mechanism In Fig. 4 of the drawing; I have diagrammatically shown the manner in which the solenoid 54 may be connected into a conventional motor circuit. Reference numeral 5! designates the main power lines, reference numerals 53 and 51 designate the main and starting windings respectively of the motor and numeral 59 designates the usual starting relay which closeslthe switch 6| during the the field winding 51.

3 initial starting period when the flow of current through the motor ileld is the greatest. The solenoid B4 is connected in the starting circuit in such a manner that upon the starting winding I 51 being cut out by the switch 8| a small amoun of current will flow through the solenoid II and The amount o. current which flows through the solenoid M is merely enough to lift the pin 62. The solenoid E8 is not strong enough to hold the switch 6| closed except during the initial starting period.

In Fig. 3 of the drawing 1'. have shown an alternative arrangement for lifting a divider block holding pin 8b. In order to simplify the description, the same reference numerals have been used in all figures of the drawing for designating like parts. In the modification shown in Fig. 3 of the drawing the pin 60 is arranged to engage within the hole t provided in the upper side of the divider bloclr 2b. The eccentric portion 2% and shaft it are provided with a conventional spiral oil feed groove 82 which serves to feed lubricant upwardly along the motor shaft into the cavity 64 formed in the bearing portion It. Lubricant from the cavity 84 is fed into the chamber 66 through the lubricant passage 68 which is arranged as shown. The pinto is carried by and preferably forms an integral part of a piston 10 which is arranged to slide within the bore 32 pro vided in an enlarged portion on the frame i2 as shown. A. spring '74 biases the piston It downwardly but is not strong enough to overcome the normal force of the lubricantwithin the chamber 66 during full speed operation of the compressor shaft. The pin 80 and the piston it are provided with a central passage 80 which serves to permit a small amount of lubricant to escape from the chamber 88 into the spaceabove the piston 10. The upper end of the bore 12 is closed by the element 82 which is also provided with a small leak port 86. By virtue of the above described arrangement, the pin W is held up by the lubricant whenever the compressor is operating at or near full speed but moves down into latching position immediately upon the compressor stopping or operating at an abnormally low speed. The force required to lift the pin 80 is so small that it is not necessary to provide an auxiliary oil pump for operating the unloader.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. A fluid compressor including a stationary member having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means for driving said rotatable member, means including a blade slidably mounted in one of said members intermediate said inlet and said outlet ports for causing fluid to be compressed between said mem- .bers during normal running operation of said compressor. means for biasing said blade into sealing engagement with the other of said members. gravity latch means for catching the blade in its retracted position and holding the blade out of sealing engagement with said other member during the starting period of operation of said compressor, and means for releasing said gravity latch means after the compressor has attained its said normal running operation.

2. A fluid compressor including a stationary member having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means for driving said rotatable member, means including a blade slidably mounted in one of said members intermediate said inlet and said outlet ports for causing fluid to be compressed between said members during normal running operation of said compressor, means for biasing said blade into sealing engagement with the other of said members, vertically movable latch means for catching the blade in its retracted position and holding the blade out of sealing engagement with said other member during the starting period of operation of said compressor, and means for moving said latch means out of blade catching and holding position at the time said compressor attains its said normal running operation.

3. A fluid compressor including a stationary member having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means for driving said rotatable member, means including a blade slidably mounted in one of said members intermediate said inlet and said outlet ports for causing fluid to be compressed between said members during normal running operation of said com :essor, means for biasing said blade into sealing engagement with the other of said members, means for catching the blade in its retracted position and holding the blade out of sealingengagement with said other member during the starting period of operation of said compressor, means for supplying electrical energy to said driving means, and electrical means connected in circuit with said driving means for moving said blade catching means out of said holding position thereof after the compressor has attained its said normal running operation.

4. A fluid compressor including a stationary member having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means for driving said rotatable member, means including a blade slidably mounted in one of said members intermediate said inlet and said outlet ports for causing fluid to be compressed between said members during normal running operation of said compressor, means for biasing said blade into sealing engagement with the other of said members, means for catching the blade in its retracted position and holding the blade out of sealing engagement with said other member during the starting period of operation of said compressor, said blade catching means being movable in one direction and in another direction, said blade catching means being gravity operated in said one direction of movement thereof, and magnetic means for operating said blade catching means in the said another direction of movement thereof after the compressor has attained its said normal running operation.

5. A fluid compressor including a stationary member having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means for driving said rotatable member, means including a blade slidably mounted in one of said members intermediate said inlet and said outlet ports for causing fluid to be compressed between said members during normal running operation of said comwannapressor, means for biasing said blade into sealing engagement with the other of said members, means for catching the blade in its retracted position and holding the blade out of sealing engagement with said other member during the starting period of operation of said compressor, said last named means comprising a gravity operated latch adapted to engage within a recess provided in the upperside of said blade, and means for moving said latch out of blade catching and holding position at the time said compressor attains its said normal running operation.

6. In a rotary compressor, a, cylinder block having a compression chamber therein and inlet and outlet ports communicating with said chamber, arotor arranged within said compression chamber, means including a blade slidably mounted in said block intermediate said inlet and said outlet ports and movable into contact with said rotor for causing fluid to be compressed in said chamber during normal running operation of said compressor, spring means for normally holding said blade in contact with said rotor, said blade having an aperture in its upper surface, a gravity operated pin disposed above said aperture for dropping into said aperture when said blade is in a retracted position so as to latch said blade in said retracted position during the starting period of operation of said compressor, and means for lifting said pin out of the aperture in said blade at the time said compressor attains its said normal running operation.

7. In a rotary compressor, a cylinder block having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotor arranged within said compression chamber, means including a blade slidably mounted in said block intermediate said inlet and said outlet ports and movable into contact with said rotor for causing fluid to be compressed in said chamber during normal running operation 01 said compressor, spring means for normally holding said blade in contact with said rotor, said blade having an aperture in its upper surface, a

gravity operated pin disposed above said aperture for dropping into said aperture when said blade is in a retracted position so as to latch said blade in said retracted position during the starting period of operation of said compressor, means for lifting said pin out of said aperture, a motor for operating said compressor having a main winding, a starting winding and a solenoid operated switch for controlling the flow of current through said starting winding, and means rendered efl'ec tive by said solenoid operated switch for controlling operation of said pin lifting means at the time said compressor attains its said normal running operation.

8. A fluid compressor including a stationary member having a compression chamber therein, an inlet port and an outlet port communicating with said chamber, a member rotatable within said chamber, means for driving said rotatable member, a blade slidably mounted in one of said members-intermediate said ports, means biasing said blade into sealing engagement with the other of said members during normal running operation of saidcompressor to cause fluid to be compressed between said members, means movable in one direction for catching said blade in its retracted position as said compressor stops operating and holding the blade out of sealing engagement with said other member during the starting period of operation of said compressor, said blade catching means being movable in another direction for releasing said blade after the compressor has attained its said normal running operation, and electrical means associated with said. blade catching means for operating the same in one of its directions or movement.

JOHN M. MURPHY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

